5.18 Configuration, Features and Runtime Options

Why is my Guile different from your Guile? There are three kinds of
possible variation:

build differences — different versions of the Guile source code,
installation directories, configuration flags that control pieces of
functionality being included or left out, etc.

differences in dynamically loaded code — behaviour and features
provided by modules that can be dynamically loaded into a running Guile

different runtime options — some of the options that are provided for
controlling Guile's behaviour may be set differently.

Guile provides “introspective” variables and procedures to query all
of these possible variations at runtime. For runtime options, it also
provides procedures to change the settings of options and to obtain
documentation on what the options mean.